1. Field of the Invention
The present invention relates to anaerobically curable compositions based on (meth)acrylate-functionalized poly(acrylate) polymers.
2. Brief Description of Related Technology
Anaerobic adhesive compositions generally are well-known. See e.g., R. D. Rich, “Anaerobic Adhesives” in Handbook of Adhesive Technology, 29, 467-79, A. Pizzi and K. L. Mittal, eds., Marcel Dekker, Inc., New York (1994), and references cited therein. Their uses are legion and new applications continue to be developed.
Conventional anaerobic adhesives ordinarily include a free-radically polymerizable acrylate ester monomer, together with a peroxy initiator and an inhibitor component. Oftentimes, such anaerobic adhesive compositions also contain accelerator components to increase the speed with which the composition cures.
For certain commercial applications, apart from that technology disclosed in U.S. Pat. No. 5,116,558 (Wrobel), conventional anaerobically curable compositions ordinarily do not develop the physical property profile to satisfy performance standards of customers. One such commercial application is a gasketing application.
Certain polyacrylate materials have been designed and developed by Kaneka Corporation for photocurable applications. The route by which these materials are synthesized involves the use of copper (I) salt catalysts, such as copper halides like copper chlorides, copper bromides and copper iodides, which despite extensive purification measures, carry over as impurities at significant concentrations in commercially available polyacrylate materials, such as those referred to by Kaneka under the trade designation XMAP and/or Telechelic polyacrylates. Copper (I) salt impurities such as these lead to poor stability in anaerobically curable compositions. These synthetic routes—commonly referred to as atom transfer radical polymerization or ATRP—are believed to be similar to those described for instance in U.S. Pat. Nos. 5,312,871 (Mardare) and 5,763,548 (Matyjaszewski). Certain polyacrylate materials have been designed and developed by Kaneka Corporation for photocurable applications. The route by which these materials are synthesized involves the use of complexed copper halide catalysts, which despite extensive purification measures, carry over as impurities at significant concentrations in commercially available polyacrylate materials, such as those referred to by Kaneka under the trade designation XMAP and/or Telechelic polyacrylates. Copper compound impurities such as these lead to poor stability in anaerobically curable compositions. These synthetic routes are believed to be similar to those described for instance in U.S. Pat. Nos. 5,312,871 (Mardare) and 5,763,548 (Matyjaszewski). See also H. Tang et al., “Highly Active Catalyst for AGET ATRP Tertiary Amine as Reducing Agent”, Polym. Preprints, 47(1), 156 (2006), in which the issues attendent with residual copper catalyst from ATRP syntheses are highlighted.
To date, again, apart from that technology disclosed in the '558 patent, it is not believed that an anaerobically curable composition based on (meth)acrylate-functionalized poly(acrylate)s suitable for gasketing applications has been successfully offered for sale commercially or described in the literature. Cf. THREE BOND product no. 1133EC, which is believed to be a polyester-urethane-methacrylate-based composition. Accordingly, it would be desirable for anaerobically curable compositions to be suitable in terms of physical property profile so that they may be viable candidates to satisfy performance standards of customers for gasketing applications.